1. FIELD OF THE INVENTION
The present invention relates to a bleaching detergent composition, containing sodium percarbonate stably incorporated therein stably, and, more particularly, it relates to a powdery bleaching detergent composition comprising a powdery detergent having a particular particle size distribution, low contents of heavy metals and sodium percarbonate of a particular particle size distribution.
2. DESCRIPTION OF THE PRIOR ART
Though the process of mixing a detergent with sodium percarbonate for providing a better bleaching effect is known, the thus obtained mixture is inferior in its storage stability and during storage it loses available oxygen to reduce its bleaching capacity. This storage stability largely depends on the ambient temperature, the humidity in air and the moisture in the detergent, etc.
The powdery detergent products available in the Japanese market are generally highly porous and, different from the products of high apparent densities, they are more susceptible to temperature changes. Thus, a special caution is required to protect sodium percarbonate from a hot and humid climate.
Powdery detergents generally contain moisture in some amount, which will depend on the method of preparation, from the time of manufacture. In a territory such as Japan where the ambient humidity fluctuates largely and the mean ambient temperature is relatively high, the detergent particles repeatedly absorb and evaporate moisture so that an equilibrium is attained between the ambient moisture and the moisture in the detergent particles, and this equilibrium moisture varies in a range of from several percents to ten or more percents.
Though the bleaching effect of sodium percarbonate when it is used in a washing process at a low temperature is relatively excellent and its stability is high when the moisture content in the detergent is small, it becomes remarkably unstable when the moisture content in the detergent is increased. On the other hand, sodium perborate, also known as an oxidant-type bleaching agent, is often incorporated with a detergent and is considerably good in its storage stability, but it cannot accomplish a sufficient bleaching effect unless it is used at a high temperature above 60.degree.C.